Such a firearm generally comprises a receiver; a barrel mounted with one end on the receiver; in this end a chamber to house a cartridge, a breech equipped with a loading lever mounted, in a way so that it can slide, in the receiver in the prolongation of the barrel between an open position enabling a cartridge to be loaded into the chamber of the barrel and a closed position pressed against the barrel; a bolt associated with the breech enabling the cartridge to be locked in the chamber; and at least one return spring to return the breech to its closed position.
Such a rifle is loaded by the movement of the breech from the back to the front, i.e. from the open position of the breech to the closed position of the breech under the effect of the return spring.
This movement of the breech carries a new cartridge from the magazine or a new cartridge placed manually in front of the chamber of the barrel in order to introduce it into the chamber. This movement also brings about the rotation of the bolt to lock the cartridge in the chamber before firing.
The reverse movement of the breech from the front to the back, i.e. the backward movement, unlocks the cartridge in the chamber of the barrel and extracts this cartridge from the chamber in order to be able to put a new cartridge in the chamber or to enable maintenance of the weapon.
The backward movement of the breech can be effected manually by operating the loading lever to empty the weapon or to feed a new cartridge into the chamber, or automatically or semi-automatically by using the pressure of the gases developed by the combustion of the powder in the cartridge during firing.
To effect the backward movement, the user must overcome the tensile force of the return spring.
In known weapons, the return spring is a conventional compression spring whose resistance to the backward movement increases progressively during the backward movement towards the rear, requiring an increasing effort.
This increasing effort generally leads to a lack of comfort and a loss of stability between shots.
The patent application GB09914 of 1912 discloses a fire arm utilising a return spring for the breech, fixed with one end to the breech and with the other end to a fixed shaft, the spring having the form of a torsion spring formed by a flat strip wound around a shaft in the form of a spiral, the windings not being in mutual contact in order for the spring to exert a torsion.
The return spring disclosed in GB 09914 is complex to manufacture, the cross-section of the strip not being constant. The pulling force exerted by the spring is moreover not constant.